You receive an HTTP Error 401.1 error when accessing a SharePoint 2007 or SharePoint 2010 site on a web front end

When attempting to view a MOSS (SharePoint) 2007 or SharePoint 2010 site locally from a Web Front End (WFE) you get an error stating: “HTTP Error 401.1 – Unauthorized: Access is denied due to invalid credentials.”

I have noticed that this happens on Windows 2003/2008 Server SP1/SP2/R2 when using Host Headers and Alternate Access Mappings on a web application in MOSS 2007. If you can access the site from remote machines and cannot access the site from the server itself, then this might be your issue.

For all my newer farm installs this includes SharePoint 2007 (MOSS) and SharePoint 2010. I use method number 2 on all SharePoint and SQL Servers in the farm.

If you cannot access the web site locally or remotely from other machines then there is an issue with security on the site and/or possibly a Kerberos related security issue

I implemented fix #2 listed in the following Microsoft KB Article. I implemented this fix on all servers in the MOSS 2007 Farm (WFE’s and Indexing/Search Server).

If using method 1, you would add all Host Headers and Alternate Access Mappings for all web applications to the BackConnectionHostNames value, then you will be able to access the sites locally from the WFE’s.

indeed MOSS 2007 is a very powerful tool with all the features and functions but one thing i really hate about it is that most of the times it's asking for too much… just right during the installation there are lots of errors, error this, error that, error, error and error! and then after so many errors there you are with your MOSS 2007 and then you try to use some of its features and again there's the never ending error again… I don't know what with the Microsoft Corporation… even when passing documents again errors! i hate it!

Actually this should be installed on every machine including production if you are using host headers or alternate access mappings. I always use the second method. The only situation where I would use method one is when SharePoint external.